I have a new gas FHA furnace, with direct-vent, etc. And so, outside my house, about 3' above the ground, is the exhaust vent. a 3" (or is it 4") open hole facing sideways coming out of my house.
What's to keep a sorts of vermin from going inside? I don't run the system AT ALL in the summer. I know it's a sealed system, but what's to keep them from wandering into the hoses (and even the heat chamber), nesting, and leaving debris that will mess up the furnace when it fires up in the fall? Shouldn'i put some screening over it?